PROJECT SUMMARY/ABSTRACT The average American undergoes nine surgical or interventional procedures over their lifetime, many related to diseases of the digestive track or conditions associated with obesity. Despite being common, most of these procedures have not been subjected to rigorous evaluation of their effectiveness. In addition, the best practices needed to accomplish the best outcomes, population-level results, patient-reported perspectives, and cost considerations have yet to be addressed. As healthcare systems strive to deliver greater value and increase the effectiveness of the care they deliver, addressing these gaps is critical. One reason for the shortfall in rigorous clinical research in gastrointestinal conditions commonly treated with surgery is a paucity of formal training in health services, clinical trials, and comparative effectiveness research for surgeons. To address this need, we propose the continuation of the University of Washington's T32 fellowship in clinical, health services, and comparative effectiveness research for surgeons. This fellowship involves didactic training and practical experience in advanced clinical research methodology focused on interventions related to the gastrointestinal system, diabetes, and obesity-related conditions. The training is focused in 6 areas (research using observational data, patient-centered outcome and preference assessment, health economics and behavioral economics in healthcare, implementation and health system science, clinical trials, and research operations management) and is intended to develop surgeon-scholars who will be successful scientists and leaders in academic medicine. The didactic component includes coursework that results in a Master of Public Health or Master of Science degree. Trainees complete a set of projects and studies using the full spectrum of research methods and approaches. The trainee's experience is fostered by a structured mentorship program, led by investigators who have a career commitment to training and demonstrated success in high-level research and integrating evidence into practice. Many of the projects led by fellows involve collaboration with a unique, statewide data sharing network of 45 hospitals and a national research platform of over 40 hospitals in 15 states. These networks allow for observational cohort studies and support the conduct of randomized trials in the management of common gastrointestinal conditions (e.g., appendicitis and diverticulitis). Trainees participate in the fellowship for two years and then serve an additional 3-5 years of clinical training. Past and current fellows have had high levels of research success judged by publications and presentations, and the program has had a considerable impact on trainees, the community, and the nation. Prior trainees who have completed their clinical training are now taking academic positions and have been finding success as independent investigators. The significant changes planned for the training in this cycle include a greater focus on clinical trials and learning health systems research related to gastrointestinal conditions. This emphasis parallels the increased number of funded RCTs and health system science studies being led by the mentors.